Battery management system with adiabatic switched-capacitor circuit

ABSTRACT

An apparatus for switching between powering a load from a battery and powering the load from another power source includes a battery manager and a switched-capacitor network, wherein the switched-capacitor network comprises a plurality of capacitors, first and second switch sets, and a controller, wherein the controller causes the switched-capacitor network to transition between a first state and a second state.

RELATED APPLICATIONS

This application claims the benefit of the Mar. 11, 2016 priority dateof U.S. Provisional Application 62/306,749, the contents of which areherein incorporated by reference.

FIELD OF INVENTION

This invention relates to power conversion, and in particular, tobattery-managers that use switched-capacitors.

BACKGROUND

Many portable electrical devices are used while the device is pluggedinto an AC source. During this time, a battery manager must providepower to both charge the battery, if necessary, and to operate thedevice itself. When the AC source is disconnected, the battery managermust switch over so that the battery provides power to the device.

SUMMARY

In one aspect, the invention features an apparatus for switching betweenpowering a load from a battery and powering the load from an AC source.Such an apparatus includes a battery manager with an AC/DC converterconnected to its input. Either the AC/DC converter or the batterymanager includes an adiabatic switched-capacitor network. Such a networkis characterized by having a capacitor with charge stored thereoncircuitry for constraining a rate of change of the charge at least inpart as a result of causing charge to pass through an inductance.

In another aspect, the invention features an apparatus for switchingbetween powering a load using energy stored in a battery and poweringthe load using energy from an AC source, the apparatus comprising abattery manager, a switched-capacitor network, a battery charger forcharging the battery while the load is being powered using energy fromthe AC source, and a first controller, wherein the battery managercomprises an input terminal for coupling to a bridge rectifier, whereinthe switched-capacitor network comprises a plurality of capacitors andfirst and second switch sets, wherein closing switches in the firstswitch set and opening switches in the second switch set arranges thecapacitors into a first state, wherein closing the switches in thesecond set and opening the switches in the first set arranges thecapacitors in a second state, and wherein, in operation, the controllercauses the switched-capacitor network to transition between the firststate and the second state at a specific frequency, thereby transferringcharge between capacitors and terminals of the switched-capacitornetwork.

In some embodiments, the switched-capacitor network is in the AC/DCconverter. Among these are embodiments in which the switched-capacitornetwork includes a controller, a charge pump, and a switching regulatorconnected to the charge pump and to a bridge rectifier. In theseembodiments, the controller controls the switching regulator and thecharge pump.

In other embodiments, the AC/DC converter is part of the batterymanager. There are a variety of locations in which one can place theswitched-capacitor network within a battery manager.

In one of these embodiments, the battery manager comprises an inputconnected to the AC/DC converter, and a step-down converter. In theseembodiments, the switched-capacitor network is between the step-downconverter and the input.

In another of these embodiments, the battery manager comprises, inaddition to a step-down converter, an input connected to the AC/DCconverter, an output connected to a load, a first line that connects theinput to the output, a second line that connects the step-down converterto the first line at a first node, a third line that connects the switchto the first line at a second node, and a switch that selectivelyconnects and disconnects the battery from the first line. In theseembodiments, the switched-capacitor network is on the first line betweenthe first and second nodes.

In another of these embodiments, the battery manager includes, inaddition to a step-down converter and a battery charger, a first lineextending between the step-down converter and an output to which a loadto be driven is to be connected, and a second line that connects thebattery charger to the first line at a first node. In these embodiments,the switched-capacitor network is disposed between the first node andthe step-down converter.

In another of these embodiments, the battery manager includes, inaddition to a step-down converter, a first line that extends frombattery manager's input to its output, and a second line that connectsthe step-down converter to the first line at a node. In theseembodiments, switched-capacitor network is disposed between the batterymanager's input and the node.

In another of these embodiments, the battery step-down converter has aninductance upon the switched-capacitor network relies to limit a rate ofchange of charge present on a capacitor within the switched-capacitornetwork.

Further embodiments include those in which the switched-capacitornetwork comprises a charge pump, a switching regulator connected to thecharge pump, and a controller that controls the switching regulator andthe charge pump so as to achieve operation thereof.

In any of the foregoing embodiments, it is possible for theswitched-capacitor network to include a charge pump and an inductancecoupled to the charge pump. Among these are embodiments in which thecharge pump comprises a cascade multiplier.

In another aspect, the invention features an apparatus for switchingbetween powering a load from a battery and powering it load from a DCsource. Such an apparatus includes a battery manager having an switchedcapacitor network that includes a capacitor having an amount of chargestored thereon, and circuitry for constrains a rate at which the amountof charge is changed at least in part as a result of causing charge topass through an inductance.

Among these embodiments are those in which the battery manager includesan input, and a step-down converter with the switched-capacitor networkbetween them.

Also among these embodiments are those in which the battery managerincludes an input, an output, a first line, a second line, a third line,a step-down converter, and a switch. In these embodiments, the output isconfigured to be connected to a load that is to be driven, the input isconnected to a DC source, the switch selectively connects anddisconnects the battery from the first line, the first line connects theinput to the output, the second line connects the step-down converter tothe first line at a first node, wherein the third line connects theswitch to the first line at a second node, and the switched-capacitornetwork is on the first line between the first and second nodes.

In yet other embodiments, the battery manager includes a first line, asecond line, an output to which a load to be driven is to be connected,a battery charger, and a step-down converter. In these embodiments, thefirst line extends between the step-down converter and the output, thesecond line connects the battery charger to the first line at a firstnode, and the switched-capacitor network is disposed between the firstnode and the step-down converter.

In some embodiments, the battery manager comprises the battery chargerand a step-down converter. Among these are embodiments in which thestep-down converter is disposed such that, in operation, energy forcharging the battery and energy for powering the load both pass throughthe step-down converter, and other embodiments in which it is insteaddisposed such that, in operation, energy for charging the battery passesthrough the step-down converter and energy for powering the loadbypasses the step-down converter.

Also among the embodiments are those that include a bypass switchcontrol circuit to control slew rate of voltage transitions in theswitched-capacitor circuit.

In still other embodiments, the battery manager includes an input, anoutput, a step-down converter, a first line, and a second line. In suchembodiments, the first line extends from the input to the output, thesecond line connects the step-down converter to the first line at anode, and the switched-capacitor network is disposed between the inputand the node.

Still other embodiments are those in which the battery manager includesa step-down converter. In these embodiments, the step-down converterincludes an inductance, and the switched-capacitor network relies on theinductance of the step-down converter to limit a rate of change ofcharge present on a capacitor within the switched-capacitor network.

Yet other embodiments include a travel charger, with the battery managerbeing a constituent thereof.

Among any of the foregoing embodiments are those in which theswitched-capacitor network includes a charge pump and an inductancecoupled to the charge pump. These include embodiments in which thecharge pump includes a cascade multiplier. Also among the foregoingembodiments are those in which the switched-capacitor network isadiabatic and those in which it is diabatic.

These and other features of the invention will be apparent from thefollowing detailed description and the accompanying figures, in which:

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a two-stage power conversion circuit;

FIG. 2 shows the circuit of FIG. 1 with additional circuitry forreceiving an AC voltage;

FIG. 3 shows a first embodiment of a switched-capacitor architecture foruse in the power-conversion circuits of FIGS. 1 and 2;

FIG. 4 shows a switching circuit contained in the stages of the powerconversion circuit of FIG. 3;

FIG. 5 is a parts list for the embodiment shown in FIG. 3;

FIG. 6 is a variant of the switched-capacitor architecture of FIG. 3with circuitry for controlling slew rate;

FIG. 7 shows operation of switches shown in FIG. 5 for controlling slewrate;

FIG. 8 shows details of a slew-rate control circuit from theswitched-capacitor architecture shown in FIG. 6;

FIG. 9 shows slew control carried out by the slew-rate control circuitryshown in FIG. 6;

FIG. 10 shows several locations for incorporation of an adiabaticswitched-capacitor circuit into a first embodiment of a battery manager;

FIG. 11 shows several locations for incorporation of an adiabaticswitched-capacitor circuit into a second embodiment of a batterymanager;

FIG. 12-15 show battery managers with an adiabatic switched-capacitorcircuit at four of the locations shown in FIGS. 10-11;

FIG. 16 is a functional block diagram of a typical adiabaticswitched-capacitor circuit;

FIG. 17 shows exemplary components for implementing an adiabaticswitched-capacitor circuit;

FIGS. 18-20 show an implementation of the step-down converter of FIGS.10-11 that includes an adiabatically charged switched-capacitor network;

FIG. 21 is a cascade multiplier for use as a switched-capacitor networkin the embodiments of FIGS. 18-20; and

FIG. 22 shows the circuit of FIG. 2 incorporated into a travel adapter.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of power convertercircuits and processing performed by and on such power convertercircuits, it should be appreciated that, in effort to promote clarity inexplaining the concepts, reference is sometimes made herein to specificswitched-capacitor circuits or specific switched-capacitor circuittopologies. It should be understood that such references are merelyexemplary and should not be construed as limiting.

As used herein, ac-dc converters are the same as AC/DC converters; andswitched-capacitor circuits are the same as switched-capacitor networksand charge pumps.

FIG. 1 shows a two-stage power conversion circuit 11 having a firstterminal 12 that connects to a first stage and a second terminal 14 thatconnects to a second stage. The first terminal 12 is at a first voltageV1 and the second terminal 14 is at a second voltage V2.

In the illustrated embodiment, the first stage is implemented as aswitch-mode pre-regulator 16 and the second stage is implemented as anadiabatic switched-capacitor circuit 18. However, in alternativeembodiments, this second stage is non-adiabatic, or diabatic.

The pre-regulator 16 can be implemented in a variety of ways, so long asthe essential function thereof, namely regulation of an output voltage,can be carried out. In the illustrated embodiment, the pre-regulator 16includes a pre-regulator switch S0, a transformer T0, a diode D0, and afilter capacitor CX. A particularly useful implementation of apre-regulator 16 is a magnetically-isolated converter, an example ofwhich is a fly-back converter.

A variety of fly-back converters can be used to implement thepre-regulator 16. These include a quasi-resonant fly-back converter, anactive-clamp fly-back converter, an interleaved fly-back converter, anda two-switch fly-back converter.

Other examples of magnetically-isolated converters are forwardconverters. Examples of suitable forward converters include amulti-resonant forward converter, an active-clamp forward converter, aninterleaved forward converter, and a two-switch forward converter.

Yet other examples of magnetically-isolated converters are half-bridgeconverters and full-bridge converters. Examples of half-bridgeconverters include an asymmetric half-bridge converter, a multi-resonanthalf-bridge converter, and an LLC resonant half-bridge converter.Examples of full-bridge converters include an asymmetric full-bridgeconverter, a multi-resonant full-bridge converter, and an LLC resonantfull-bridge converter.

It is also possible to implement the pre-regulator 16 using anon-isolated converter. Examples include a buck converter, a boostconverter, and a buck-boost converter.

As used herein, two functional components are said to be “isolated,” ormore specifically, “galvanically isolated,” if energy can becommunicated between those components without a direct electricalconduction path between those components. Such isolation thuspresupposes the use of another intermediary for communicating energybetween the two components without having actual electrical currentflowing between them. In some cases, this energy may includeinformation.

Examples include the use of a wave, such as an electromagnetic,mechanical, or acoustic wave. As used herein, electromagnetic wavesinclude waves that are in span the visible range, the ultraviolet range,and the infrared range. Such isolation can also be mediated through theuse of quasi-static electric or magnetic fields, capacitively,inductively, or mechanically.

Most functional components have circuitry in which different parts ofthe circuit are at different electrical potentials. However, there isalways a potential that represents the lowest potential in that circuit.This is often referred to as “ground” for that circuit.

When a first and second functional component are connected together,there is no guarantee that the electrical potential that defines groundfor the first component will be the same as the electrical potentialthat defines ground for the second circuit. If this is the case, and ifthese components are connected together, it will be quite possible forelectrical current to flow from the higher of the two grounds to thelower of the two grounds. This condition, which is called a “groundloop,” is undesirable. It is particularly undesirable if one of the twocomponents happens to be a human being. In such cases, the current inthe ground loop may cause injury.

Such ground loops can be discouraged by galvanically isolating the twocomponents. Such isolation essentially forecloses the occurrence ofground loops and reduces the likelihood that current will reach groundthrough some unintended path, such as a person's body.

The switched-capacitor circuit 18 can be implemented as aswitched-capacitor network. Examples of such networks include laddernetworks, Dickson networks, Series-Parallel networks, Fibonaccinetworks, and Doubler networks. These can all be adiabatically chargedand configured into multi-phase networks. A particularly usefulswitched-capacitor network is an adiabatically charged version of afull-wave cascade multiplier. However, diabatically charged versions canalso be used.

As used herein, changing the charge on a capacitor “adiabatically” meanscausing an amount of charge stored in that capacitor to change bypassing the charge through a non-capacitive element. A positiveadiabatic change in charge on the capacitor is considered adiabaticcharging while a negative adiabatic change in charge on the capacitor isconsidered adiabatic discharging. Examples of non-capacitive elementsinclude inductors, magnetic elements, resistors, and combinationsthereof. In either case, the result is a constraint on the rate at whichthe quantity of charge on the capacitor can change.

In some cases, a capacitor can be charged adiabatically for part of thetime and diabatically for the rest of the time. Such capacitors areconsidered to be adiabatically charged. Similarly, in some cases, acapacitor can be discharged adiabatically for part of the time anddiabatically for the rest of the time. Such capacitors are considered tobe adiabatically discharged.

Diabatic charging includes all charging that is not adiabatic anddiabatic discharging includes all discharging that is not adiabatic.

As used herein, an “adiabatic switched-capacitor circuit” is a networkhaving at least one capacitor that is both adiabatically charged andadiabatically discharged. A “diabatic switched-capacitor circuit” is anetwork that is not an adiabatic switched-capacitor circuit.

Examples of pre-regulators 16, switched-capacitor circuits 18, theiraccompanying circuitry, and packaging techniques can be found U.S. Pat.Nos. 9,362,826, 9,497,854, 8,723,491, 8,503,203, 8,693,224, 9,502,968,8,619,445, 9,203,299, and 9,041,459, U.S. Patent Publications2016/0197552, 2015/0102798, 2014/0301057, 2013/0154600, 2015/0311786,2014/0327479, 2016/0028302, 2014/0266132, 2015/0077175, and2015/0077176, and PCT publications WO2014//062279, WO2015//138378,WO2015//138547, WO2016//149063, and WO 2017/007991, the contents ofwhich are herein incorporated by reference.

Adiabatic switched-capacitor circuits are described in detail in U.S.Pat. No. 8,860,396, issued Oct. 14, 2014, in U.S. ProvisionalApplications 62/132,701 and 62/132,934, both of which were filed on Mar.13, 2015. The contents of the foregoing documents are incorporatedherein by reference.

A first controller 20 controls the operation of the first and secondstages. The first controller 20 includes a primary side 22 that controlsthe first stage and a secondary side 24 that controls the second stage.An isolation barrier 26 separates the primary side 22 from the secondaryside 24.

The primary side 22 of the first controller 20 controls thepre-regulator switch S0. Opening and closing the pre-regulator switch S0controls the current provided to a primary side of the transformer T0.This, in turn, controls the voltage across the filter capacitor CX. Whenthe pre-regulator switch S0 is on, the diode D0 is off and when thepre-regulator switch S0 is off, the diode D0 is on.

The pre-regulator 16 also includes a regulator-output terminal 28maintained at an intermediate voltage VX1 that is lower than the firstvoltage V1. This regulator-output terminal 28 connects to the adiabaticswitched-capacitor circuit 18. The adiabatic switched-capacitor circuit18 thus receives this intermediate voltage VX1 and transforms it intothe second voltage V2.

The adiabatic switched-capacitor circuit 18 operates in discrete steps.Thus, it only provides coarse regulation of its output. It cannotprovide fine regulation of its output. It is for the pre-regulator 16 tocarry out this fine regulation. The two-stage design shown in FIG. 1reduces the need for the pre-regulator 16 to sustain a high-currentburden. This means that the secondary winding of the transformer T0 caninstead carry a much smaller RMS current. This, in turn, lowers windingloss and reduces the voltage ripple at the regulator-output terminal 28.It also means that the filter capacitor CX that couples thepre-regulator 16 to the adiabatic switched-capacitor circuit 18 can bemade smaller.

However, the improved performance of the pre-regulator 16 cannot becompletely offset by the increased size and power loss of having theadiabatic switched-capacitor circuit 18 in the second stage. Therefore,it is imperative that the adiabatic switched-capacitor circuit 18 beboth extremely efficient and small.

The two-stage power conversion circuit 11 in FIG. 1 is shown as beingconfigured to receive a DC voltage. In an alternative embodiment shownin FIG. 2, a bridge rectifier 65 coupled to the first terminal 12 by acoupling capacitor CB provides a way to receive an AC voltage VAC.

The power conversion circuit 10 of FIG. 2 is similar to that shown inFIG. 1, but with additional circuitry for receiving an AC voltage VACprovided by an AC source 4 and converting that AC voltage VAC into thesecond voltage V2. The AC voltage VAC is provided to input terminals ofa bridge rectifier 65 having bridge diodes DB1, DB2, DB3, and DB4arranged to form a bridge and having an output across a bridge capacitorCB. The output across the bridge capacitor CB becomes the first voltageV1 presented at the first terminal 12. A power-conversion circuit 10 ofthis type may be incorporated into a travel adapter 13, as shown in FIG.22. Such a travel adapter 13 outputs a DC voltage at a USB port 15.

Some embodiment include circuitry for controlling harmonic current andthus boosting the ratio of real power to apparent power that flowsthrough the power supply. This is particularly useful for power suppliesthat attach to a wall outlet that supplies an AC voltage. An example ofsuch circuitry is an active power-factor corrector 67 disposed betweenthe bridge rectifier 65 and the pre-regulator 16.

FIG. 2 also shows a fuse 61 between the AC power source 4 and theremaining components of the power-conversion circuit 10 for safety. Anelectromagnetic interference filter 63 is also provided to suppress theuncontrolled emission of electromagnetic waves that may arise duringoperation of the power-conversion circuit 10.

FIG. 3 shows a first embodiment of a switched-capacitor circuit 18 thatis designed to accept a nominal voltage of 20 volts and to produce avariety of output voltages, such as 5 volts and 10 volts. This isparticularly useful for Type-C travel adapters. This is because, unlikethe older USB standards, in which the output is always five volts, thenewer USB Type C standard permits higher output voltages, such as ten,fifteen, and even twenty volts.

FIG. 3 shows a first embodiment of an adiabatic switched-capacitorcircuit 18 that is designed to accept a nominal voltage of 20 volts. Theillustrated adiabatic switched-capacitor circuit 18 features a firstswitched-capacitor stage 32, a second switched-capacitor stage 34, afirst bypass switch S1, a second bypass switch S2, and a third bypassswitch S3. An LC filter having an output inductor L1 and an outputcapacitor C0 permit adiabatic operation. By selectively opening andclosing the bypass switches S1, S2, S3, it is possible to selectivelybypass selected ones of the first and second switched-capacitor stages32, 34.

Each of the first and second stages 32, 34 is a 2× voltage dividerhaving a maximum voltage conversion from VX1 to VX2 of 4:1. Theresulting adiabatic switched-capacitor circuit 18 is designed to acceptan intermediate voltage VX1 of 20 volts and to provide a voltage ofeither 20 volts, 10 volts, or 5 volts. Some embodiments deliver a15-volt output voltage, which is sometimes required by the Type-Cstandard. This can be provided by having the pre-regulator 16 deliver 15volts to the switched-capacitor circuit 18 instead of 20 volts andrunning the switched-capacitor circuit 18 in the 1:1 mode.

The adiabatic switched-capacitor circuit 18 shown in FIG. 3 has threemodes of operation, a 1:1 mode, a 2:1 mode, and a 4:1 mode. In the 1:1mode, the first bypass switch S1 closes, and the second and third bypassswitches S2 and S3 open. In the 2:1 mode, the second bypass switch S2closes and the first and third bypass switches S1 and S3 open. In the4:1 mode, the third bypass switch S3 closes and the first and secondbypass switches S1 and S2 open. All bypassed stages run in a low-powermode to save power since they are not needed to provide voltageconversion (i.e., they are not switching at a specific frequency).

FIG. 4 illustrates a switched-capacitor circuit 36 inside the firststage 32. A similar circuit is within the second stage 34. Duringoperation, this circuit transitions between first and second states. Inthe first state, all switches labeled “1” close and all switches labeled“2” open. In the second state, all switches labeled “1” open and allswitches labeled “2” close. The switched-capacitor circuit 36 alternatesbetween the first and second state at a specific frequency. Thisfrequency is one that is selected to produce a second intermediatevoltage VX2 that is half of the intermediate voltage VX1.

FIG. 5 shows a component list for one implementation of the adiabaticswitched-capacitor circuit 18 shown in FIG. 3. The components wereselected so the solution provides a high efficiency, a small solutionsize, and a maximum output voltage ripple of 100 mV peak-to-peak. Thetotal value column specifies the total amount of inductance and/orcapacitance required of the components at their operating condition.

In an alternative embodiment, the first and second bypass switches S1,S2 can be turned on and off in such a way that the second voltage V2slews up and down in a controlled manner. This is particularly usefulwhen there is a maximum slew rate to be met. For example, in the case ofa Type-C USB power adapter, where the second voltage V2 is programmablefrom 5 volts to 20 volts, there is a maximum slew-rate requirement of 30mV/μs for voltage transitions.

FIG. 6 shows an alternative embodiment of the adiabaticswitched-capacitor circuit 18 of FIG. 3 in which first and second bypassswitch control circuits 42 are added to control the slew rate of voltagetransitions in the adiabatic switched-capacitor circuit 18 shown in FIG.3. These bypass switch control circuits 42 control the slew rate ofvoltage transitions in the adiabatic switched-capacitor circuit 18 shownin FIG. 3 when the output transitions from 5 volts to 10 volts and from5 volts to 20 volts. The bypass switch control circuit 42 also controlsthe second voltage V2 slew-rate from 10 volts to 5 volts and 20 volts to5 volts.

FIG. 7 shows a table of bypass switch states for three different voltageoutputs.

Referring to FIG. 6, to output 20 volts, one asserts a first controlinput V20. To output only 10 volts, one asserts a second control inputV10. By default, when neither the first nor the second output isasserted, the adiabatic switched-capacitor circuit 18 outputs 5 volts.

FIG. 8 shows details of a bypass switch control circuit 42 shown in FIG.6. Although the second bypass switch S2 is shown in FIG. 8, the firstbypass switch S1 is controlled in a similar way. All of the bypassswitches S1, S2, and S3 are N-channel FETs (NFETs). The compositeback-to-back NFET configuration for the second and third bypass switchesS2, S3 is necessary to block the flow of reverse current from the outputto the input when these switches are off while the first bypass switchS1 is on. Although the second and third bypass switches S2, S3 aredepicted as discrete back-to-back NFETs in FIG. 8, these devices may bereplaced by a single transistor with an adaptive body switch in a fullyintegrated solution.

A first slew-control switch S8 in FIG. 8 turns off the first and secondbypass switches S1, S2 by shorting their gate and source terminals. Wheneither the first bypass switch S1 or the second bypass switch S2 isturned on, the first slew-control switch S8 (in the respective control)circuit opens, and the second voltage V2 transitions from 5 volts to 10volts or from 5 volts to 20 volts. Meanwhile, an anti-slewing capacitorC6 and a constant current source I1 control the upward slew rate of thesecond voltage V2 transition from 5 volts to 10 volts or 20 volts.

When the first and second bypass switches S1, S2 are turned off and thesecond voltage V2 transitions from 10 volts to 5 volts or 20 volts to 5volts, a second slew-control switch S9 turns on and allows a bleederresistor R1 to discharge the anti-slewing capacitor C6. This controlsthe downward slew rate of the second voltage V2.

A comparator in FIG. 6 detects when the second voltage V2 has droppedbelow a certain threshold VTH (e.g., VTH=5.25 V) and terminates thedischarge of the anti-slewing capacitor C6 by opening the secondslew-control switch S9. Note that the bleeder resistor R1 may bereplaced by a current source, and the slew rates of both positive andnegative voltage transitions may be programmed by making the currentsource I1, the bleeder resistor R1, and the anti-slewing capacitor C6 beprogrammable or re-configurable.

When 20 volts is desired at the output, the second and third bypassswitches S2, S3 are off while the first bypass switch S1 is on. Thefirst and second (2:1) switched-capacitor stages are also off. The firstbypass switch S1 is an N-channel FET (NFET) whose turn-on is controlledby the current source I1, which is a constant current source, and theanti-slewing capacitor C6 such that the second voltage V2 slews up at afixed rate.

During the 5-volt to 20-volt transition, the first and secondslew-control switches S8, S9 are open and the first bypass switch S1acts as a source-follower. In this configuration, the voltage on thesource of the first bypass switch S1 follows the voltage on its gate,which is given by the current though the current source I1 divided bythe capacitance of the anti-slewing capacitor C6. Initially, when thefirst bypass switch S1 turns on and the second voltage V2 slews up, thefirst bypass switch S1 operates in the saturation region (i.e.,V_(DS)>V_(GS)−V_(T), where V_(T) is the NFET's threshold voltage). Asthe output approaches its final level, the first bypass switch S1transitions into the linear region and acts as a low-impedance switch. AZener diode D1 clamps the gate-to-source voltage (V_(GS1)) of the bypassswitch S1 to a safe level (e.g., V_(GS1) equals 5 volts) duringsteady-state operation. The transition from 20 volts back to 5 volts iscontrolled by the bleeder resistor R1, which discharges the outputcapacitance in a slew-rate controlled manner.

When 10 volts is desired at the output, the first and third bypassswitches S1, S3 are off while the second bypass switch S2 is on. Thefirst (2:1) switched-capacitor stage is on and the secondswitched-capacitor stage is off. The second bypass switch S2 includesback-to-back NFETs, that operate as a source follower when the secondvoltage V2 transitions from 5 volts to 10 volts. As describedpreviously, the current source I1 and anti-slewing capacitor C6 controlthe slew rate of the second voltage V2 as it transitions from 5 volts to10 volts, the bleeder resistor R1 controls the transition from 10 voltsback to 5 volts, and the Zener diode D1 clamps the gate-to-sourcevoltage of the second bypass switch S2 to a safe level duringsteady-state operation at 10 volts (i.e. V2).

Although not explicitly shown in FIGS. 6 and 8, it should be understoodby those skilled in the art that additional circuitry is useful toprotect the system against various single-point failures and faultconditions such as over-current, over-temperature, and over-voltage onany and all nodes, switches, and passive components.

FIG. 9 shows typical voltage transitions for the switched-capacitorcircuit with slew-rate limited bypass switch control in a Type-C USBpower adapter. The second voltage V2 slews up and down at approximately20 mV/μs. According to the USB PD specification, the load must be in alow-power standby state during voltage transitions. For the simulationresults shown in FIG. 9, the load was turned on after the output settledto its final level.

FIG. 10 illustrates a first battery manager 60A that provides energy topower to a load 8 while also providing energy for charging a battery BATusing power delivered from an ac-dc converter 10 connected to an ACsource 4. The first battery manager 60A supplies a system voltage VSYSfor powering the load 8. It does so even when the ac-dc converter 10 isdisconnected from the battery manager 60A.

The AC source 4 need not be a wall-source. Instead, the AC source 4 canbe part of a wireless charging system for charging the device. Such awireless charging system typically includes a base station and a deviceto be charged. The base station receives AC at a first frequency andprovides it to a frequency-converter that steps it up to a higherfrequency and provides it to a first coil. The device to be chargedincludes a second coil selected such that, when brought in proximitywith the first coil, the two form an air-core transformer. This permitsenergy provided by the first coil to be made available at the secondcoil so that it can be used to charge the battery on the device to becharged.

The conversion to a higher frequency is useful for ensuring that thefirst coil can be made a reasonable size. Typical output frequencies arein the range of 50 kHz. Various standards exist for the extent of thefrequency transition and the amount of voltage and/or current providedby the base station. An example of such a standard is the QI standard.

The first battery manager 60A includes a step-down converter 56 thattransforms a second voltage V2 provided by the ac-dc converter 10 intothe system voltage VSYS. It also includes a constant-current/constantvoltage (CCCV) charger 52 that provides power for charging the batteryBAT. The charger 52 includes circuitry for maintaining either a constantcurrent or a constant voltage while charging of the battery, formeasuring the amount of charge on the battery, and for providingprotection from faults. The step-down converter 56 can either be a partof a device powered by the battery or it can be placed outside such adevice. A battery switch S4 selectively connects and disconnects thebattery BAT from the load 8. A second controller 64 synchronizesoperation of the step-down converter 56 and the charger 52.

When the ac-dc converter 10 connects to an AC source 4, the battery BATis not needed for supplying power to the load 8. Accordingly, the secondcontroller 64 opens the battery switch S4. Meanwhile, the step-downconverter 56 lowers the second voltage V2 to a value a little above thecharging voltage of the battery BAT, thereby allowing the CC/CV charger52 to charge the battery efficiently, assuming the battery is notalready fully charged. The step-down converter 56 also provides thenecessary system voltage VSYS to the load 8.

However, once the ac-dc converter 10 is disconnected, the step-downconverter 56 can no longer supply power. The second controller 64therefore closes the battery switch S4 so that the battery BAT cansupply the necessary system voltage VSYS.

FIG. 11 illustrate a second battery manager 60B, where the chargingvoltage and system voltage VSYS are separated, unlike in the firstbattery manager 60A. The battery switch S4 is only closed when thebattery is used as a source of power for the system voltage VSYS. Theadvantage of this second battery manager 60B over the first batterymanager 60A is that the step-down converter 56 does not have to supplypower to charge the battery BAT and the system voltage VSYS when theac-dc converter 10 is connected.

In some embodiments, the ac-dc converter 10 includes an adiabaticallycharged switched-capacitor converter of the type illustrated in FIGS.2-4 and variants thereof.

FIGS. 10 and 11 collectively show first through eighth locations P1, P2. . . P8 in which an adiabatic switched-capacitor circuit 18 of the typeshown in FIG. 3 can be placed within the first and second batterymanagers 60A, 60B. More than one adiabatic switched-capacitor circuit 18can actually be used, however, the largest performance improvement willlikely be seen by only incorporating a single adiabaticswitched-capacitor circuit 18.

FIG. 12 shows a third battery manager 70A in which the adiabaticswitched-capacitor circuit 18 is placed at the first location P1.Incorporating an adiabatic switched-capacitor circuit 18 into the thirdbattery manager 70A reduces the burden on the step-down converter 56.For example, in the third battery manager 70A, shown in FIG. 12, thevoltage stress is about half of what it would have been had theadiabatic switched-capacitor circuit 18 been omitted. This has theeffect of drastically reducing the power loss in the step-down converter56 for a given output power.

FIG. 13 shows a fourth battery manager 70B in which the adiabaticswitched-capacitor circuit 18 is instead placed at the sixth locationP6. Placement of the adiabatic switched-capacitor circuit 18 provides away to target the part of the circuit in which improvement is sought.For example, in the fourth battery manager 70B, shown in FIG. 13, themain improvement is not in the step-down converter 56, but in thedownstream point-of-load (POL) converters in a load 8.

The configurations shown in FIGS. 12 and 13 are particularly usefulbecause they are most compatible with existing integrated circuits thatimplement battery managers.

FIG. 14 shows a fifth battery manager 70C in which the adiabaticswitched-capacitor circuit 18 has been placed in the second position P2.FIG. 15 shows a sixth battery manager 70D in which the adiabaticswitched-capacitor circuit 18 has been placed in the fifth position P5.

FIG. 16 shows a block diagram of a typical adiabatic switched-capacitorcircuit 18. The circuit is a 2× voltage divider that provides a 2:1voltage conversion from an input voltage VX3 to an output voltage V3.This adiabatic switched-capacitor circuit 18 is designed to accept amaximum input voltage of 24 volts.

FIG. 17 shows an example component list for the architecture in FIG. 16.

A typical step-down converter 56 as shown in FIGS. 10-11 generallyincludes a switching regulator. Accordingly, some embodimentsincorporate a switched-capacitor converter 86 in the step-down converter56 together with a third controller 84 that controls both theswitched-capacitor converter 86 and the built-in switching regulator 88.The third controller 84 can thus operate the switched-capacitorconverter 86, as shown in FIG. 18, in such a way that the switchingregulator 88 adiabatically charges and discharges the capacitors withinthe switched-capacitor converter 86. This provides a way to achieveadiabatic charge and discharge without the need to provide an extra LCfilter with the switched-capacitor converter 86. Additionally, theswitched-capacitor converter 86 in this case is inherently modular andcan readily be supplied as a separate component to be incorporated in anexisting step-down converter 56.

FIGS. 19-20 illustrate two additional architectures that implement thesame concept. The embodiment shown in FIG. 19 is the reverse of theembodiment in FIG. 18. While the embodiment shown in FIG. 20, providesan efficient way to convert power by placing the switching regulator 88in series with the input of the switched-capacitor converter 86 and inparallel with the output of the switched-capacitor converter 86.Therefore, the switching regulator 88 only carries a fraction of thecurrent delivered to the output while still retaining the ability todirectly control the current delivered to the output.

The third controller 84 in the embodiments of FIGS. 18-20 providescontrol signals to turn the switches within the switching regulator 88and the switched-capacitor converter 86 on and off in response to asensed output voltage VO and/or input voltage VI. Based on these inputs,the controller 84 makes necessary adjustments to the control signalsprovided to switching regulator 88 and to the switched-capacitorconverter 86 such that the such that the output voltage VO is regulatedwithin some tolerance.

In the illustrated embodiments, the switching regulator 88 is a Buckconverter that includes a first switch SA, a second switch SB, and aninductor L2. When the first switch SA is closed, the second switch SB isopen, and vice versa. The first and second switches SA, SB operate at aspecific frequency. This frequency controls an average dc currentthrough the inductor L2. This makes it possible to control the voltageat the output terminal of the inductor L2 (i.e., the terminal notconnected to the switches) by varying the duty cycle of the first switchSA. In particular, the longer the first switch SA is closed during acycle the lower the voltage at the output terminal of the inductor L2will be.

FIG. 21 illustrates a detailed circuit diagram of one implementation inwhich the switched-capacitor converter 86 is a full-wave cascademultiplier. The switched-capacitor converter 86 includes a first set 1of switches, a second set 2 of switches, and capacitors C1A-C3B. Closingswitches in the first switch set 1 and opening switches in the secondswitch set 2 arranges the capacitors C1A-C3B are arranged in a firststate. Conversely, closing the switches in the second set 2 and openingthe switches in the first set 1 arranges the capacitors C1A-C3B in asecond state. During normal operation, the switched-capacitor converter86 cycles between the first state and the second state at a specificfrequency, thereby transferring charge between the capacitors C1A-C3Band terminals. The switched-capacitor converter 86 can be modeled as adc transformer as in FIGS. 18-20. In this implementation, the voltageconversion ratio (VH to VL) is three to one.

In some implementations, a computer-accessible storage-medium includes adatabase representative of one or more components of the converter. Forexample, the database may include data representative of a switchingnetwork that has been optimized to promote low-loss operation of acharge pump.

Generally speaking, a computer-accessible storage-medium may include anynon-transitory storage media accessible by a computer during use toprovide instructions and/or data to the computer. For example, acomputer accessible storage medium may include storage media such asmagnetic or optical disks and semiconductor memories.

Generally, a database representative of the system may be a database orother data structure that can be read by a program and used, directly orindirectly, to fabricate the hardware comprising the system. Forexample, the database may be a behavioral-level description orregister-transfer level (RTL) description of the hardware functionalityin a high level design language (HDL) such as Verilog or VHDL. Thedescription may be read by a synthesis tool that may synthesize thedescription to produce a netlist comprising a list of gates from asynthesis library. The netlist comprises a set of gates that alsorepresent the functionality of the hardware comprising the system. Thenetlist may then be placed and routed to produce a data set describinggeometric shapes to be applied to masks. The masks may then be used invarious semiconductor fabrication steps to produce a semiconductorcircuit or circuits corresponding to the system. In other examples,Alternatively, the database may itself be the netlist (with or withoutthe synthesis library) or the data set.

Having described the invention, and a preferred embodiment thereof, whatis claimed as new, and secured by Letters Patent is: 1-68. (canceled)69. An apparatus comprising a battery manager, a switching network, abattery charger for charging a battery, and a first controller, whereinsaid battery manager comprises an input terminal for coupling to anAC/DC converter, wherein said switching network comprises first andsecond switch sets, wherein said switching network, when connected to acapacitor set that comprises a capacitor, forms a switched-capacitornetwork, wherein closing switches in said first switch set and openingswitches in said second switch set arranges said capacitor set into afirst state, wherein closing said switches in said second set andopening said switches in said first set arranges said capacitor set intoa second state, and wherein, in operation, said controller causes saidswitched-capacitor network to transition between said first state andthe second state at a specific frequency, thereby transferring chargebetween said capacitor set and terminals of said switched-capacitornetwork.
 70. The apparatus of claim 69, wherein said battery managercomprises said switched-capacitor network.
 71. The apparatus of claim69, wherein said battery manager comprises an input and a step-downconverter, wherein said input is connected to said AC/DC converter, andwherein said switched-capacitor network is between said step-downconverter and said input.
 72. The apparatus of claim 69, wherein saidbattery manager comprises a step-down converter connected to said inputterminal and to said switched-capacitor network and a switch thatselectively connects and disconnects a battery from saidswitched-capacitor network and from an output terminal of said batterymanager.
 73. The apparatus of claim 69, wherein said battery managercomprises a step-down converter connected between said input terminaland said switched-capacitor network and a switch that selectivelyconnects and disconnects said battery from said switched-capacitornetwork and an output of said battery manager.
 74. The apparatus ofclaim 69, wherein said switched capacitor-network connects to an inputterminal of said battery manager and wherein said battery managerfurther comprises a step-down converter that connects to saidswitched-capacitor network and to an output terminal of said batterymanager and a switch that selectively connects said battery to saidswitched-capacitor network and to said output terminal.
 75. Theapparatus of claim 69, wherein said battery manager comprises astep-down converter, wherein said step-down converter comprises aninductance, and wherein said switched-capacitor network relies on saidinductance of said step-down converter to limit a rate of change ofcharge present on said capacitor.
 76. The apparatus of claim 69, whereinsaid AC/DC converter comprises said first controller, a charge pump, anda switching regulator connected to said charge pump, wherein said firstcontroller controls said switching regulator and said charge pump. 77.The apparatus of claim 69, wherein said switched-capacitor networkcomprises a charge pump and an inductance coupled to said charge pump.78. The apparatus of claim 69, further comprising rate-controlcircuitry, wherein during operation of said switched-capacitor network,said capacitor has an amount of charge stored thereon, and wherein saidrate-control circuitry is configured to constrain a rate at which saidamount of charge is changed at least in part as a result of causingcharge to pass through an inductance.
 79. The apparatus of claim 69,wherein said battery is configured to receive energy wirelessly from anAC source.
 80. The apparatus of claim 69, wherein said battery chargerswitches between attempting to maintain a constant current while chargeis being provided to said battery and attempting to maintain a constantvoltage while charge is being provided to said battery.
 81. Theapparatus of claim 69, further comprising a travel charger, wherein saidbattery manager is a constituent of said travel charger.
 82. Theapparatus of claim 69, wherein said battery-charger is a CCCV charger.83. The apparatus of claim 69, wherein said controller comprises anisolation barrier between a primary and secondary section thereof. 84.The apparatus of claim 69, wherein said switched-capacitor network isone that, during operation thereof, causes said capacitor to experiencea change in charged stored therein by causing charge to be passedthrough a non-capacitive element.
 85. The apparatus of claim 69, furthercomprising a travel adapter, wherein said AC/DC converter is aconstituent of said travel adapter, wherein said travel adaptercomprises a USB port, and wherein said travel adapter receives an ACvoltage and outputs a DC voltage at said USB port.
 86. The apparatus ofclaim 69, wherein said battery manager comprises said battery chargerand a step-down converter, wherein said step-down converter is disposedsuch that, in operation, energy for charging said battery and energy forpowering said load both pass through said step-down converter.
 87. Theapparatus of claim 69, wherein said battery manager comprises saidbattery charger and a step-down converter, wherein said step-downconverter is disposed such that, in operation, energy for charging saidbattery passes through said step-down converter and energy for poweringsaid load bypasses said step-down converter.
 88. The apparatus of claim69, further comprising a bypass switch control circuit to control slewrate of voltage transitions in said switched-capacitor circuit.